public static int migratoryBirds(List<Integer> arr) {
    List<Integer> typeCountArray=new ArrayList<>();
    int countMax=0;
    for(int i=1;i<6;i++){
        int typeCount=0;
        for(int j=0;j<arr.size();j++){
            if(arr.get(j)==i) typeCount++;
        }
        if(typeCount>countMax) countMax=typeCount;
        typeCountArray.add(typeCount);
    }
    int type=0;
    for(int i=0;i<typeCountArray.size()+1;i++){
        if(typeCountArray.get(i)==countMax){
            type=i+1;
            break;
        } 
    }
  return type;  
}

C# solution:

    public static int migratoryBirds(List<int> arr)
{
    int result = 0;
    List<int> x = new List<int>() {0,0,0,0,0};

    for (int i=0; i<5; i++) {
        for (int j=0; j<arr.Count; j++) {
            if(arr[j] == i+1) {
                x[i]++;
            }
        }
    }

    result = Result.maxValMinIndex(x) + 1;

    return result;
}

public static int maxValMinIndex(List<int> arr) {
    int maxVal = 0;
    int index = 0;

    for(int i=0; i<arr.Count; i++) {           
        if(i==0 || arr[i] > maxVal) {
            maxVal = arr[i];
            index = i;
        }
    }     
    return index;
}

Solution in R:

Note that array indices begin at 1 in R.

migratoryBirds <- function(arr) {
    t <- table(arr)
    mode <- names(t[t == max(t)])
    return(mode[1])
}

//Java 8 Map map=new HashMap<>(); for(int i = 0;i

JavaScript solution:

function migratoryBirds(arr) {
    // only birds type 1 - 5. create an array of zeros, and remember
    // arrays start at 0. so bird type 4 would be birdsCount[3].
    const birdsCount = new Array(5).fill(0);
    
    // loop through arr and increment count based on arr[i] - 1.
    // why arr[i] - 1? again, because arrays start at 0.
    for (let i = 0; i < arr.length; i++) {
        birdsCount[arr[i] - 1] += 1;
    }
    
    // now determine out of the birdsCount, which one has the largest count?
    const maxCount = Math.max(...birdsCount);
    
    // using maxCount, which index in birdsCount appears first?
    // remember the index is bird type - 1. cause again, arrays start at 0.
    const firstIndex = birdsCount.indexOf(maxCount);
    
    // using the index found, add 1.
    // why add 1? look at the first comment.
    return firstIndex + 1;
}